A three-dimensional well group structure for in-situ remediation of groundwater and an application method thereof

Abstract

The present invention discloses a three-dimensional well group structure for in-situ groundwater remediation and an application method, which relates to the technical field of groundwater remediation. The well group structure includes an air compressor, a PLC controller, a chemical dosing device, groundwater wells and submersible pumps. The well group structure and application method of the present invention greatly improve the efficiency and effect of groundwater remediation. By adopting a unique cross 3D hydraulic circulation mode, not only a small hydraulic circulation is formed within the well itself, but also a large hydraulic circulation is formed among the well groups. In this way, small hydraulic circulations are nested within the large hydraulic circulation. In the large circulation, there is both horizontal hydraulic transfer and hydraulic jump transfer between upper and lower layers, making the chemical diffusion more uniform and extensive, capable of expanding the effective coverage radius, far exceeding the coverage range of traditional single wells, greatly reducing the demand for the number of well groups, reducing the construction and operation and maintenance costs, and being applicable to the remediation of structures contaminated in complex scenarios such as gas stations, operating chemical enterprises, and roads in chemical industrial parks.

Description

Technical Field

[0001] The present invention relates to the technical field of groundwater remediation, and specifically provides a three-dimensional well group structure for in-situ groundwater remediation and an application method thereof. Background Art

[0002] In modern society, as an important part of water resources, the protection and remediation of groundwater quality have attracted increasing attention. Groundwater aquifers are vulnerable to various pollutants, leading to the deterioration of their water quality, which seriously threatens the ecological environment and human health. When traditional groundwater remediation technologies are used to repair groundwater pollution, they mainly adopt the high groundwater well injection technology, and inject agents into the underground aquifer through the groundwater well injection technology to repair the groundwater layer.

[0003] Traditional groundwater remediation technologies have many limitations when dealing with aquifer pollution. Taking the common groundwater well injection technology as an example, the interval between injection wells is small, and the diffusion of agents is only under the action of concentration and water level pressure difference in the well, with poor diffusion effect, slow speed and uneven distribution. The diffusion radius of agents in a single well is extremely limited, usually only 3 - 5 meters. Therefore, in a large polluted area, in order to achieve effective remediation, it is necessary to densely build a large number of wells, which undoubtedly greatly increases the remediation cost and project complexity.

[0004] Especially in the scenario of chemical enterprises in production, due to the layout limitations of buildings and underground complex pipelines, when the aquifer under the building or structure is polluted, it is extremely difficult to add agents to this area. Traditional technologies are difficult to ensure the effective diffusion of agents to the core polluted area and cannot fully play the remediation role, resulting in the groundwater remediation work in such special areas being in trouble and difficult to achieve the expected remediation goal, seriously restricting the process and effect of groundwater pollution control. Therefore, it is necessary to propose a three-dimensional well group structure for in-situ groundwater remediation and an application method thereof to solve the problems in the prior art. Summary of the Invention

[0005] The purpose of the present invention is to make up for the deficiencies of the prior art, and provides a three-dimensional well group structure for in-situ groundwater remediation and an application method thereof. It can pump the lower-layer water to the upper layer, the upper-layer water to the lower layer, and achieve three-dimensional circulation between the well pipe itself and adjacent well pipes, so that the agent is fully mixed and contacted with the groundwater, realizing the efficient removal of organic pollutants in the groundwater and improving the remediation effect on groundwater.

[0006] To solve the above technical problems, the present invention provides the following technical solution: A three-dimensional well group structure for in-situ groundwater remediation, the well group structure includes an air compressor, a PLC controller, a chemical agent dosing device, a groundwater well, and a groundwater pump;

[0007] The groundwater well is a specially made stainless-steel well pipe, which is composed of two layers. The inner layer is 304 stainless steel with slits, and the outer layer is a stainless-steel wire mesh structure. The space between the two layers is filled with gravel and quartz sand with a particle size of 2-3 mm. The entire well pipe is a permeable structure. There is an intermediate barrier in the middle position of the well pipe, which divides the well pipe into upper and lower parts, and the middle is an impermeable structure;

[0008] The submersible pump includes a pump body, which is suspended in the groundwater well by a steel wire rope. The bottom end of the pump body is provided with a feed inlet, and the feed inlet is immersed in the groundwater. The outer surface of the pump body is provided with a water outlet pipe. The end of the water outlet pipe away from the pump body penetrates through the intermediate barrier and extends to the other side of the intermediate barrier. The outer surface of the pump body is provided with a chemical dosing pipe. The top end of the chemical dosing pipe is connected to a chemical dosing device. The upper surface of the pump body is fixedly communicated with an air inlet pipe and an air outlet pipe, and the top ends of the air inlet pipe and the air outlet pipe are both connected to an air compressor. Solenoid valves are installed inside the air inlet pipe and the air outlet pipe, and the solenoid valves are connected to a PLC controller through wires.

[0009] Further, the width of the slits in the inner layer of the groundwater well is 0.5-1.5 mm, the slits are evenly distributed and the distance between adjacent slits is 5-10 mm. The mesh size of the stainless-steel wire mesh structure in the outer layer of the groundwater well is 1-3 mm. The intermediate barrier is made of rubber and has a thickness of 5-10 mm.

[0010] Furthermore, the chemical dosing pipe is made of polyvinyl chloride and has an inner diameter of 3-5 mm. A sealing gasket made of rubber is provided at the connection part between the chemical dosing pipe and the pump body.

[0011] Furthermore, a piston slides sealingly inside the pump body, and a spring is installed on the bottom surface of the piston.

[0012] Furthermore, a hollow limiting ring is installed on the inner wall of the feed inlet. The upper surface of the hollow limiting ring is connected to the bottom end of the spring. A spherical ball is arranged inside the hollow limiting ring, and when the spherical ball is located at the bottom of the hollow limiting ring, it keeps sealing with the inner wall of the feed inlet.

[0013] An application method of a three-dimensional well group structure for in-situ groundwater remediation, the method includes the following steps:

[0014] S1. Well group construction and equipment installation: According to the characteristics, scope and hydrogeological conditions of the groundwater pollution area, determine the location and quantity of the groundwater wells, and plan the layout to ensure full coverage and efficient treatment of the pollution area. When excavating the well holes, strictly control the verticality error within ±0.5°, and its diameter should match the well pipe specifications and meet the construction standards;

[0015] S2. System debugging and parameter setting: Thoroughly check the appearance of the equipment, component connections, and electrical system. Set the opening and closing times of the solenoid valves of the chemical dosing device and the electronic valves of the underground water pumps according to the pollution degree, pollutant characteristics, and treatment objectives. When testing water pumping and chemical dosing, if the water pumping of the water pump is unstable, fine-tune the opening time of the intake air solenoid valve by 0.5 seconds each time until it is stable, so that the variation range of the water pumping pressure is within ±0.1 MPa and the error of the chemical flow rate is within ±5%.

[0016] S3. Groundwater circulation and purification treatment:

[0017] S301: Start the air compressor. The underground water pumps of a group of groundwater wells pump the lower-layer water and discharge it from the upper layer, and the other group pumps the upper-layer water and discharges it from the lower layer. Each pump accurately doses chemicals through the chemical dosing pipe at the set rate. The chemicals and groundwater are mixed in the underground water pump. Within the same group of groundwater wells, the groundwater circulates between the upper and lower layers through the well pipe's water permeability and the flow direction of the incoming and outgoing water. Due to the changes in water level and water pressure, after the lower-layer water is pumped up into the upper layer, part of it permeates through the upper layer and part diffuses to the surrounding area, and part re-enters the pump for circulation. After the upper-layer water flows down to the lower layer, a similar circulation occurs, forming a small hydraulic circulation within the well.

[0018] S302. Between the two groups of groundwater wells, the cooperation of pumping the upper layer and discharging the lower layer and pumping the lower layer and discharging the upper layer is carried out. According to the water level difference, water flow inertia, and pumping power, a large hydraulic circulation is constructed. The water discharged from the groundwater well that pumps the lower layer and discharges the upper layer will flow horizontally towards the suction area of the groundwater well that pumps the upper layer and discharges the lower layer. Along the way, it carries the chemicals and infiltrates the formation. Part of the groundwater enters the lower layer of the groundwater well that pumps the lower layer and discharges the upper layer and then undergoes an upward pumping cycle. The water discharged from the lower layer of the groundwater well that pumps the upper layer and discharges the lower layer will flow back horizontally in the reverse direction to the suction area of the groundwater well that pumps the lower layer and discharges the upper layer, and infiltrate the surrounding formation through the permeable structure. Part of the groundwater enters the upper layer and then undergoes a pumping cycle again. In this process, the large cycle nests the small cycle, the horizontal water flow carries the chemicals and spreads horizontally, and the alternating pumping and discharging of the upper and lower layers achieve hydraulic jump transfer, forming a cross 3D hydraulic connection, so that the chemicals are evenly diffused in the rock and soil gaps between the two wells and react fully with the pollutants to purify the groundwater.

[0019] S303. For special repair technology requirements, for the catalytic oxidation technology, inject oxidation agents into one group of groundwater wells and catalytic agents into another group of groundwater wells, and control the injection rate to ensure that the two are mixed in a ratio of 1:0.5 - 1:2 in the circulating water flow between the two groups of wells, so as to ensure efficient reaction in a short time after the agents come into contact and give full play to the catalytic oxidation effect to degrade pollutants. For the treatment of chlorinated hydrocarbons by the oxidation + reduction technology, first inject reduction agents into one group of groundwater wells for dechlorination bioreduction treatment, and set the treatment duration to 12 - 48 hours according to the pollution concentration. Then inject oxygen-rich clean water into the groundwater wells for 6 - 12 hours to increase the oxidation-reduction potential. Then inject slow-release oxidation agents from another group of groundwater wells for oxidation treatment. The release rate of the slow-release oxidation agents is adjusted to 0.01 - 0.1 grams per hour per cubic meter according to the remaining pollutant amount and formation characteristics. By optimizing the injection sequence and rate of the agents, the repair efficiency is improved. According to water quality monitoring and pump operating conditions, use the PID algorithm to fine-tune the electronic valve switch of the groundwater pump in a timely manner to maintain stable and efficient operation.

[0020] S4. Water quality monitoring and system optimization: Regularly collect water samples to measure pollutant concentration, acidity and alkalinity, dissolved oxygen, and conductivity indicators, and optimize the system according to the results. When the pollution does not meet the standard, analyze the reasons and make adjustments. If the agents are not good, first try to replace them in small doses, observe the water quality for 1 - 2 days to determine whether to replace them completely, and reset the dosing rate when replacing. If the abnormal water flow affects the diffusion and circulation of the agents, fine-tune the pumping frequency of the pump, and continuously monitor and optimize until the water quality meets the standard to ensure the repair effect and the efficient and stable operation of the well group structure.

[0021] Furthermore, in the well group construction and equipment installation steps, first lay a gravel filter layer with a thickness of 0.3 - 0.5 meters at the bottom of the well hole, then slowly place the groundwater well pipe vertically into it, install a groundwater pump in the groundwater well pipe, and firmly hang it with a steel wire rope. The inlet of the feed port is at an appropriate depth, and tightly connect the inlet pipe, outlet pipe, chemical dosing pipe, air compressor, chemical dosing device, and ground PLC controller. Each interface is sealed tightly. The inlet and outlet pipes use 10 - 20 mm stainless steel bellows, and 5 - 10 cm bentonite is filled between the well pipe and the well hole wall for reinforcement.

[0022] Even further, in the horizontal water flow transfer of the large hydraulic cycle between the two groups of groundwater wells, considering the influence of water flow on the diffusion of agents, adjust the pumping and drainage rate ratio of the two wells. When the water flow rate is low, appropriately reduce the pumping rate of the well that pumps water up and drains water down, and increase the pumping rate of the well that pumps water down and drains water up, so as to keep the horizontal hydraulic gradient between the two wells within the range of 0.005 - 0.01 m / m, and ensure that the agents can overcome the water flow resistance and fully diffuse to the area 20 - 30 meters away from the well in the horizontal direction.

[0023] Furthermore, in the hydraulic jump transfer link between the upper and lower layers, it is optimized according to the characteristics of different formation lithologies. In sandy aquifers, the large porosity is conducive to the rapid penetration of water flow and agents. The extraction frequency is set at once every 4 - 6 hours. While in silty clay aquifers, the porosity is small and the hydraulic conductivity is low. The extraction frequency is adjusted to once every 8 - 10 hours, and the extraction power is increased by 10% - 15% periodically during the extraction process, so that the agent can effectively break through the formation resistance to achieve jump transfer. And during the jump layer, if the agent concentration in the upper layer is 30% - 50% higher than that in the lower layer, the extraction parameters are automatically adjusted to slow down the pumping in the upper layer and speed up the pumping in the lower layer by 10% - 20%, balance the concentration to promote the two-way uniform diffusion of the agent, and strengthen the 3D hydraulic connection repair efficiency.

[0024] Compared with the prior art, the three-dimensional well group structure and application method for in-situ groundwater remediation have the following beneficial effects:

[0025] The well group structure and application method of the present invention greatly improve the efficiency and effect of groundwater remediation. By adopting a unique cross 3D hydraulic circulation mode, not only a small hydraulic circulation is formed within the well itself, but also a large hydraulic circulation is formed between the well groups. In such a large hydraulic circulation, a small hydraulic circulation is nested. In the large circulation, there is both horizontal hydraulic transfer and hydraulic jump transfer between the upper and lower layers, making the agent diffusion more uniform and extensive, capable of expanding the effective coverage radius, far exceeding the coverage range of traditional single wells, significantly reducing the demand for the number of well groups, lowering the construction and operation and maintenance costs, and being applicable to the pollution remediation of structures in complex scenarios such as gas stations, operating chemical enterprises, and roads in chemical industrial parks.

[0026] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 It is a schematic diagram of the application of a three-dimensional well group structure for in-situ groundwater remediation;

[0029] Figure 2 It is a three-dimensional structure schematic diagram of an underground water pump;

[0030] Figure 3Schematic diagram of the internal structure of an underground water pump;

[0031] Figure 4 is Figure 3 Schematic diagram of the partial structure of.

[0032] 1. Air compressor; 2. PLC controller; 3. Chemical dosing device; 4. Groundwater well; 401. Intermediate barrier; 5. Underground water pump; 501. Pump body; 502. Feed inlet; 503. Outlet pipe; 504. Chemical dosing pipe; 505. Steel wire rope; 506. Inlet pipe; 507. Outlet pipe; 508. Piston; 509. Spring; 510. Hollow limiting ring; 511. Sphere. Specific implementation manners

[0033] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] Embodiment 1: Remediation of groundwater pollution in a small factory area

[0035] Application scenario description

[0036] Due to long-term chemical production activities in a small factory area, its underground soil and aquifer have been severely polluted. The polluted area is about 5,000 square meters, located below the production workshop and storage area, with a depth range from 5 meters to 15 meters below the ground surface. The pollutants include residues of organic chemical raw materials (such as the concentration of benzene series substances up to 5 mg / L and the concentration of phenolic substances about 3 mg / L), heavy metal ions (the lead concentration reaches 0.2 mg / L and the cadmium concentration 0.05 mg / L), and petroleum substances (the petroleum hydrocarbon content is about 8 mg / L). The pollution degree is uneven, and the pollutant concentration in some areas far exceeds several times the environmental standard. There are dense surrounding buildings and crisscross underground pipe networks. Traditional remediation technologies are difficult to apply due to site restrictions. Not only is the remediation cost high (it is estimated that the traditional remediation cost is more than 5 million yuan), but it is also easy to cause long-term interference to production operations. There is an urgent need for an efficient and accurate remediation solution with little disturbance to the site to ensure the quality of groundwater, reduce environmental risks, and ensure the continuous compliance production of the factory and the ecological safety of the surrounding area.

[0037] Professional exploration teams use high-precision geological drilling equipment to analyze the geological structure, determine the characteristics and distribution of rock and soil layers at each level. For example, the upper layer is silty clay with a thickness of 3 - 5 meters and a permeability coefficient of about 1×10-5 cm / s; the middle sand layer is 6 - 8 meters thick with a permeability coefficient of 5×10-3 cm / s; the lower clay rock layer is 4 - 6 meters thick with a permeability coefficient of 1×10-7 cm / s. With the help of an advanced underground water flow velocity and direction meter, the water flow velocity is accurately measured in the range of 0.05 - 0.15 m / d, and the flow direction is northeast. Water samples are collected at multiple points and analyzed by precision instruments such as inductively coupled plasma mass spectrometry (ICP-MS) and gas chromatography - mass spectrometry (GC-MS) in the laboratory to accurately grasp key information such as the types and concentration distributions of pollutants. Based on this, considering the surrounding buildings, underground pipelines and water flow characteristics, 8 groundwater wells 4 are carefully designed in a circular layout at reasonable positions around the polluted area, and the well spacing is optimized to 20 - 30 meters according to hydrogeological parameters and pollution distribution, laying a solid foundation for subsequent precise remediation.

[0038] Strictly select the appropriate drilling equipment according to the plan, accurately excavate well holes with appropriate depths, and use advanced total station and inclinometer to strictly control the verticality within ±0.5° and the diameter to meet the well pipe specifications. Slowly lower the special double-layer stainless steel well pipe into the hole, and lay a gravel filter layer with a thickness of 0.4 meters and a particle size of 3 - 5 mm at the bottom. Accurately install an underground water pump 5 on the upper layer of the well pipe, and firmly hang it with a high-strength corrosion-resistant steel wire rope 505. Accurately determine that the feed inlet is at a depth of 2 - 3 meters below the groundwater level. High-quality fluororubber sealing materials are used for all connection links to ensure that the air inlet pipe 506, air outlet pipe 507, and chemical agent dosing pipe are tightly connected without leakage. The air compressor 1, chemical agent dosing device 3, and ground PLC controller 2 are seamlessly connected, and the whole process is professionally monitored to ensure that the verticality of the well pipe meets the standards accurately.

[0039] Technicians conduct a comprehensive inspection and maintenance of the equipment. According to the previous exploration and treatment objectives, integrating theoretical calculations and practical experience, scientifically set the opening and closing degree range of the solenoid valve of the chemical agent dosing device 3 to 25% - 35%, and set the dosing rate to 5 - 10 L / h according to the pollutant concentration. Accurately plan the opening and closing time range of the electronic valves at the air inlet and outlet of the underground water pump 5 in the PLC controller 2 (the air inlet valve opens for 4 - 5 seconds and closes for 9 - 11 seconds; the air outlet valve opens for 7 - 8 seconds and closes for 11 - 12 seconds), conduct trial pumping and trial dosing, and closely observe the stability of the pumping pressure and flow rate and the accuracy of the chemical agent dosing flow rate with high-precision pressure sensors and electromagnetic flow meters. If the pumping pressure fluctuation exceeds ±0.1 MPa or the chemical agent flow rate error exceeds ±5%, adjust the opening and closing time of the air inlet electronic valve according to the feedback data, with an adjustment accuracy of 0.1 second each time. After repeated optimization, ensure the stable operation of the system and accurately control the chemical agent dosage and the water flow dynamic balance.

[0040] Start the air compressor 1. A group of underground water pumps 5 in the wells extract the lower-layer water to the upper layer for discharge according to the procedure, and the other group does the opposite. After each pump accurately doses the medicine, the medicine and the groundwater are instantaneously mixed in the pump. Inside the same group of wells, the groundwater circulates between the upper and lower layers through the water-permeable structure of the well pipe and the water flow guidance. Taking the well that extracts the lower-layer water and discharges it from the upper layer as an example, after the lower-layer water is pumped to the upper layer by the pump, part of it diffuses tortuously through the water-permeable structure of the upper layer and comes into full contact with the surrounding rock and soil to enhance the mixing of the medicine; part of it flows back for recirculation to form a stable small hydraulic cycle. When the upper-layer water flows downward to the lower layer, it is mixed again near the suction inlet of the pump to enhance the remediation efficiency. Specifically, the 304 stainless steel slits (slit width 1 mm, spacing 8 mm) in the inner layer of the well pipe, the outer-layer stainless steel wire mesh (mesh hole 2 mm), and the 2-3 mm gravel quartz sand layer in the middle cooperate to guide the water flow into a turbulent state, making the medicine disperse more evenly and increasing the contact probability with pollutants.

[0041] When the two groups of wells cooperate to construct a large hydraulic cycle, the drainage of the well that extracts the lower layer and discharges it from the upper layer flows horizontally to the water intake area of the well that extracts the upper layer and discharges it from the lower layer. The medicine seeps into the formation along the way, and part of the water enters the lower-layer cycle; the upper-layer drainage of the well that extracts the upper layer and discharges it from the lower layer flows reversely and back, seeps into the surrounding formation through the water-permeable structure and then enters the lower layer for extraction again. In this process, the large cycle nests the small cycle. The horizontal water flow carries the medicine and diffuses up to 20 - 30 meters. The alternating pumping and drainage of the upper and lower layers achieve hydraulic jump transfer, forming a cross 3D hydraulic connection to ensure that the medicine is evenly dispersed in the rock and soil gaps and deeply purify the groundwater. In areas with relatively fast water flow velocity in the sand layer, adjust the extraction and drainage rate according to the water flow velocity monitoring data to maintain the uniformity of the medicine concentration and the stability of the cycle; in the silty clay layer, use pulsed pressure to assist the medicine to penetrate the formation and enhance the remediation effect.

[0042] For complex organic pollutants, if catalytic oxidation technology is required, one group of wells injects oxidation medicine (hydrogen peroxide concentration 10% - 15% solution, injection rate 3 - 5 L / h), and the other group injects catalytic medicine (iron-based catalyst concentration 0.5 - 1 g / L, injection rate 2 - 3 L / h). Accurately control the rate to make the two mix in a 1:0.8 ratio in the circulating water flow between the two wells. For example, when treating benzene-series pollutant contamination, the oxidation and catalytic medicines react rapidly in the rock and soil pores and groundwater under the drive of the water flow, degrading the benzene-series substances into harmless substances. The reaction rate is 60% higher than that of traditional single-medicine injection. When treating chlorinated hydrocarbons, first inject reduction medicine (zero-valent iron dosage 10 - 15 g / L, lasting for 24 hours) in one group of wells for dechlorination bioreduction, then inject oxygen-rich clear water (dissolved oxygen content 8 - 10 mg / L, flow rate 8 - 10 L / h) to wash for 8 hours to increase the redox potential, and finally inject slow-release oxidation medicine (potassium permanganate slow-release particles, release rate 0.05 g / h·m 3 ) for oxidation treatment, and adjust the release rate according to the formation characteristics for continuous purification.

[0043] Water samples are regularly collected from the extraction wells, and professional equipment is used to accurately detect indicators such as pollutant concentration, pH value, and dissolved oxygen. After 3 months of operation, if the local purification fails to meet the standards, the reasons are deeply analyzed, such as abnormal water flow or ineffective chemicals. The pumping frequency of the water pump is adjusted accordingly, or the appropriate chemicals are replaced, and the dosing rate is reset. Continuous monitoring and optimization are carried out. After system repair, the concentration of groundwater pollutants is significantly reduced. The concentration of benzene series substances is reduced to less than 0.1 mg / L, the concentration of phenols is less than 0.05 mg / L, the content of heavy metal lead is within 0.01 mg / L, the content of cadmium is less than 0.002 mg / L, and the content of petroleum hydrocarbons reaches the standard of 0.5 mg / L. The water quality meets the industrial reuse standard, saving 800,000 yuan in water cost annually, reducing the risk of pollution discharge fines by 1.2 million yuan, reducing the hidden danger of soil pollution diffusion, protecting the surrounding ecology, enhancing the environmental reputation of the factory, and helping to expand the market and achieve sustainable development.

[0044] Example 2: Treatment of local groundwater pollution in a residential community

[0045] A professional environmental monitoring team enters the residential community and uses precise geophysical exploration equipment and geological drilling technology to accurately determine the boundary and depth range of the polluted area. The depth is approximately between 8 meters and 12 meters below the ground surface, and the area is 3,000 square meters, located under the community greening and some residential buildings.

[0046] With the help of advanced water quality analysis instruments, the water samples are comprehensively tested, and the pollutants are locked as nitrogen and phosphorus nutrients (ammonia nitrogen concentration 2 mg / L, total phosphorus 0.5 mg / L) generated by the leakage of domestic sewage, trace organic detergents (anionic surfactant content 0.3 mg / L), and heavy metals (such as lead concentration 0.08 mg / L, cadmium concentration 0.02 mg / L) infiltrated from surrounding industrial activities. Combining the building layout of the community, the underground pipe network map, and the groundwater hydrological model, 6 groundwater wells 4 are scientifically planned at key nodes around and inside the polluted area, and the layout is grid-shaped, taking into account the principle of the best repair effect and the least interference to residents' lives, ensuring the comprehensive and effective control and cyclic treatment of polluted water bodies.

[0047] Professional drilling equipment with low noise and small volume is selected for construction. The diameter and verticality of the wellbore are strictly controlled. Special double-layer stainless steel well pipes are installed in sequence, and a gravel filter layer with a thickness of 0.35 meters and a particle size of 4-6 mm is laid at the bottom to prevent the formation from blocking the well pipes. An underground water pump 5 is accurately installed in the well pipe, and it is reliably suspended with high-strength and corrosion-resistant steel wire rope 505. The feed inlet is accurately adjusted to the appropriate water level depth to ensure smooth and stable water intake. The air inlet pipe 506, the air outlet pipe 507, and the chemical dosing pipe are carefully connected, and food-grade silicone rubber sealing gaskets are used to ensure the airtight and watertightness of the connection. The air compressor 1, the chemical dosing device 3, and the ground PLC controller 2 are seamlessly docked. The verticality of the well pipe is monitored by a laser guide instrument throughout the construction process, and the error is stably controlled within ±0.5°, ensuring the stable and efficient operation of the system.

[0048] Technicians follow a strict process to comprehensively detect the electrical performance of the equipment, the integrity of the mechanical structure, and the reliability of component connections. According to the characteristics of pollutants and environmental standards, an intelligent algorithm model is used to initially set the opening and closing cycle of the solenoid valve of the chemical dosing device 3 to open for 5 minutes and close for 10 minutes, with a flow rate parameter of 3 - 6 L / h; the switching time logic of the electronic valve of the underground water pump 5 is to open for 3.5 - 4.5 seconds and close for 8.5 - 9.5 seconds at the air inlet, and open for 6.5 - 7.5 seconds and close for 9.5 - 10.5 seconds at the air outlet. Start the trial pumping and chemical dosing program, and use high-precision pressure sensors and electromagnetic flowmeters to monitor the system dynamics in real-time. If the pumping pressure fluctuation exceeds ±0.1 MPa or the chemical flow rate error exceeds ±5%, adjust the switching time of the electronic valve at the air inlet according to the feedback data, with an adjustment accuracy of 0.1 second each time. After repeated optimization, ensure the stable operation of the system and accurately control the chemical dosage and the balance of water flow dynamics.

[0049] Start the air compressor 1. The underground water pumps 5 in a group of wells efficiently extract the underlying groundwater, and after mixing with chemicals, discharge it from the upper layer, while the other group operates in the reverse direction. Within the same group of wells, the groundwater is driven by the water permeability structure of the well pipe and the water level difference, and stably circulates between the upper and lower layers. Taking the well that pumps the lower layer water and discharges it from the upper layer as an example, after the lower layer water is strongly pumped to the upper layer by the pump, part of it evenly diffuses through the stainless steel wire mesh on the outer layer of the well pipe and the intermediate filling medium, and through the diffusion and osmosis effects, fully interacts with the surrounding soil and groundwater, enhancing the chemical dispersion degree and reaction probability; part of the water returns to the pump body for recirculation, forming local turbulence inside the pump to strengthen chemical mixing and constructing an efficient small hydraulic circulation system. Specifically, the inner and outer layer structures of the well pipe and the filled gravel and quartz sand cause the water flow to alternate between laminar and turbulent states, enhancing the chemical diffusion effect and improving the remediation efficiency.

[0050] The two groups of wells cooperate with each other to build a powerful hydraulic circulation network by means of the water level gradient, water flow inertia, and pumping power difference. The water discharged from the well that pumps the lower layer and discharges it from the upper layer carries the chemicals and radiates horizontally towards the water intake area of the well that pumps the upper layer and discharges it from the lower layer. Along the way, it interacts with different permeable strata depths, and part of the water enters the lower layer of the well that pumps the upper layer and discharges it from the lower layer to participate in the circulation; the upper layer drainage of the well that pumps the upper layer and discharges it from the lower layer symmetrically returns to the upper layer of the well that pumps the lower layer and discharges it from the upper layer, penetrates the surrounding strata through the water permeability structure and then enters the lower layer for circulation, realizing an effective horizontal diffusion of 20 - 30 meters and a hydraulic jump transfer of alternating driving between the upper and lower layers, forming a cross 3D hydraulic connection, driving the deep purification of the polluted water body in the rock and soil pores between the two wells by the chemicals, and degrading the pollutant concentration. In case of a local high-permeability area in the sandy soil layer, adjust the pumping rate ratio to maintain the horizontal hydraulic gradient at 0.008 m / m to ensure uniform chemical diffusion; in the low-permeability clay layer, increase the pulsed pumping period to promote the chemical penetration through the strata and improve the remediation effect.

[0051] For heavy metal and organic compound pollution, a chemical precipitation - redox synergistic technology is adopted. Chelating agents (disodium ethylenediaminetetraacetate concentration 2 - 3 g / L, dosing rate 4 - 6 L / h) and reducing agents (sodium sulfite concentration 5 - 8 g / L, dosing rate 3 - 5 L / h) are injected into a group of wells to precipitate heavy metal ions and partially reduce high-valence metals to low-valence and easily precipitable states. A strong oxidizing agent of Fenton's reagent type (hydrogen peroxide concentration 8% - 12%, ferrous sulfate concentration 2 - 3 g / L, mixed and added at a volume ratio of 5:1, rate 4 - 6 L / h) is injected into another group of wells, and the oxidizing agent and reducing agent are controlled to be mixed at a ratio of 2.5:1 in the circulating water flow. For example, in the treatment of lead-cadmium - organochlorine compound pollution, the chelating agent captures lead and cadmium to form a precipitate, the reducing agent reduces some high-valence chromium to a precipitate, and Fenton's reagent generates strongly oxidizing free radicals to degrade organochlorine. After multiple rounds of circulation, the pollutant concentration is greatly reduced. The ammonia nitrogen concentration is reduced to below 0.2 mg / L, the total phosphorus is within 0.05 mg / L, the content of anionic surfactant is below 0.03 mg / L, the content of heavy metal lead is within 0.005 mg / L, and the cadmium content is below 0.001 mg / L, improving the water quality to meet or exceed the secondary standard of the drinking water source water quality standard, and ensuring the safety of residents' water use.

[0052] Regularly collect water samples from the extraction wells according to the specifications, and conduct full-index analysis with high-precision equipment such as inductively coupled plasma mass spectrometry (ICP-MS) and gas chromatography - mass spectrometry (GC-MS). If local water quality fluctuations are found to be unqualified during monitoring, quickly trace and investigate. If the distribution of the reagent is unbalanced due to uneven formation penetration, fine-tune the frequency of the well water pump in the corresponding area, increase or decrease the extraction volume by 10% - 20% to improve the water flow field; if the reagent precipitation blocks the formation pores, pulse-inject an appropriate amount of acidic cleaning agent (hydrochloric acid concentration 0.5% - 1%, injection volume 1 - 2 L) to dredge, and restart the cycle for repair; if the growth of microorganisms affects the repair, add a bacteriostatic agent (chlorine dioxide concentration 0.2 - 0.3 mg / L, dosing amount 0.5 - 1 L / h) to control the flora, continuously and dynamically optimize the system to ensure the stable compliance of groundwater, restore the ecological function, and improve the quality of the living environment and the health and well-being of residents in the community.

[0053] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the same elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

Claims

1. A three-dimensional well group structure for in-situ groundwater remediation, characterized in that: The well group structure comprises an air compressor (1), a PLC controller (2), a reagent dosing device (3), a groundwater well (4) and a groundwater pump (5); The groundwater well (4) is a special stainless steel well pipe, which is composed of two layers, an inner layer of 304 stainless steel with slits, and an outer layer of a stainless steel wire mesh structure. The middle of the two layers is filled with crushed stones and quartz sand with a particle size of 2-3 mm. The whole well pipe is a permeable structure. The well pipe has an intermediate blocker (401) at the middle position, which divides the well pipe into two parts, the upper and lower parts, and the middle part is a water-impermeable structure. The groundwater pump (5) comprises a pump body (501), the pump body (501) being suspended in a groundwater well (4) by means of a steel wire rope (505), a feed port (502) being arranged at the bottom end of the pump body (501), and the feed port (502) being immersed in groundwater, a water outlet pipe (503) being arranged on the outer surface of the pump body (501), an end of the water outlet pipe (503) being away from the pump body (501) passing through the intermediate barrier (401) and extending to the other side of the intermediate barrier (401), a drug dosing pipe (504) being arranged on the outer surface of the pump body (501), the top end of the drug dosing pipe (504) being connected to the drug dosing device (3), and an air inlet pipe (506) and an air outlet pipe (507) being fixedly connected to the upper surface of the pump body (501), The top end of the air inlet pipe (506) and the top end of the air outlet pipe (507) are both connected to the air compressor (1); solenoid valves are installed inside the air inlet pipe (506) and the air outlet pipe (507); and the solenoid valves are connected to the PLC controller (2) via wires; a piston (508) is sealed and slidably installed inside the pump body (501); a spring (509) is installed on the bottom surface of the piston (508); a hollow limit ring (510) is installed on the inner wall of the feed port (502); the upper surface of the hollow limit ring (510) is connected to the bottom end of the spring (509); a sphere (511) is arranged inside the hollow limit ring (510); and when the sphere (511) is located at the bottom of the hollow limit ring (510), it maintains a seal with the inner wall of the feed port (502).

2. A three-dimensional well group structure for in-situ groundwater remediation according to claim 1, characterized in that: The width of the slits in the inner layer of the groundwater well (4) is 0.5-1.5 mm, the slits are evenly distributed and the distance between adjacent slits is 5-10 mm. The mesh size of the stainless steel wire mesh structure in the outer layer of the groundwater well (4) is 1-3 mm. The intermediate barrier (401) is made of rubber and has a thickness of 5-10 mm.

3. A three-dimensional well group structure and application method for in-situ groundwater remediation according to claim 1, characterized in that: The drug dosing pipe (504) is made of polyvinyl chloride and has an inner diameter of 3-5 mm. A sealing gasket made of rubber is provided at the connection between the drug dosing pipe (504) and the pump body (501).

4. An application method of the three-dimensional well group structure for in-situ groundwater remediation according to claim 1, characterized in that: The method comprises the following steps: S1. Well group construction and equipment installation: Determine the location and number of groundwater wells based on the characteristics, scope and hydrogeological conditions of the groundwater pollution area, plan the layout to ensure comprehensive coverage and efficient treatment of the pollution area, and strictly control the verticality error within ±0.5° when digging wells. The diameter should be adapted to the well pipe specifications and meet the construction standards; S2. System debugging and parameter setting: Check the appearance of the equipment, component connections, and electrical systems in detail. Set the opening and closing time of the solenoid valve and the electronic valve of the underground water pump according to the degree of pollution, characteristics of the pollutants, and treatment targets. When testing water pumping and dosing, if the water pump is unstable, fine-tune the opening time of the air inlet electronic valve every 0.5 seconds until it is stable, so that the pumping pressure fluctuation range is within ±0.1MPa and the error of the chemical flow rate is within ±5%; S3. Groundwater circulation and purification treatment: S301: Start the air compressor (1), and the groundwater pumps of one group of groundwater wells (4) pump the lower layer water to the upper layer, and the other group pumps the upper layer water to the lower layer. Each pump accurately injects the medicine through the medicine injection pipe at a set rate. The medicine and the groundwater are mixed in the groundwater pump. In the same group of groundwater wells (4), the groundwater circulates in the upper and lower layers due to the water permeation of the well pipe and the flow direction of the inlet and outlet water. Due to the changes in water level and water pressure, after the lower layer water is pumped into the upper layer, part of it diffuses to the surrounding area through the water permeation part of the upper layer, and part of it enters the pump for circulation. After the upper layer water flows down to the lower layer, it circulates in a similar way, forming a small hydraulic circulation in the well; S302, between the two groups of groundwater wells (4), pumping up and discharging down and pumping down and discharging up are coordinated, and a large hydraulic cycle is constructed according to the water level difference, water flow inertia and pumping power. The water discharged from the pumping down and discharging up groundwater well (4) will flow horizontally to the water absorption area of ​​the pumping up and discharging down groundwater well, and carry the reagent to penetrate the stratum on the way. Part of the groundwater enters the lower layer of the pumping down and discharging up groundwater well (4) and then performs an upward pumping cycle. The water discharged from the lower layer of the pumping up and discharging down groundwater well (4) will flow back to the water absorption area of ​​the pumping down and discharging up groundwater well along the reverse horizontal flow, and penetrate the surrounding strata through the permeable structure. Part of the groundwater enters the upper layer and then pumps and circulates. In this process, the large cycle is nested in the small cycle, and the horizontal water flow carries the reagent to diffuse horizontally. The upper and lower layers are alternately pumped and discharged to realize hydraulic jump layer transmission, forming a cross 3D hydraulic connection, so that the reagent is evenly diffused in the rock and soil gap between the two wells, and fully reacts with the pollutants to purify the groundwater; S303. In response to special remediation technology requirements, for catalytic oxidation technology, an oxidizing agent is injected into one group of groundwater wells (4), and a catalytic agent is injected into another group of groundwater wells (4). The injection rate is controlled so that the two are mixed in a ratio of 1:0.5-1:2 in the circulating water flow between the two groups of wells to ensure that the agents react efficiently within a short period of time after contact, and fully exert the catalytic oxidation effect to degrade pollutants; for oxidation + reduction technology to treat chlorinated hydrocarbons, a reducing agent is first injected into one group of groundwater wells (4) for dechlorination biological reduction treatment, and the treatment time is 1:0.5-1:

2. The time is set to 12-48 hours according to the pollution concentration, and then oxygen-rich clean water is injected into the groundwater well (4) for cleaning for 6-12 hours to increase the redox point. Then, a slow-release oxidizing agent is injected from another group of groundwater wells (4) for oxidation treatment. The release rate of the slow-release oxidizing agent is controlled at 0.01-0.1 g / hour / cubic meter according to the amount of remaining pollutants and the characteristics of the formation. The repair efficiency is improved by optimizing the injection sequence and rate of the agent. According to water quality monitoring and water pump working conditions, the PID algorithm is used to fine-tune the switch of the groundwater pump electronic valve in a timely manner to maintain stable and efficient operation; S4. Water quality monitoring and system optimization: Collect water samples regularly to measure pollutant concentration, acidity, alkali, dissolved oxygen, and conductivity indicators, optimize the system based on the results, and adjust after analyzing the cause when pollution does not meet the standards. If the reagent is not good, try replacing it with a small dose first, observe the water quality for 1-2 days to decide whether to replace it completely, reset the injection acceleration rate when replacing it, and if abnormal water flow affects the diffusion and circulation of the reagent, fine-tune the pump extraction frequency, continuously monitor and optimize until the water quality meets the standards, and ensure the repair effect and efficient and stable well group structure.

5. The application method of the three-dimensional well group structure for in-situ groundwater remediation according to claim 4 is characterized in that: In the steps of well group construction and equipment installation, a 0.3-0.5 m thick gravel filter layer is first laid at the bottom of the wellbore, and then the groundwater well (4) pipe is vertically and slowly placed therein, and a groundwater pump is installed in the groundwater well (4) pipe and is securely suspended with a steel wire rope. The feed port is immersed in water at an appropriate depth, and the air inlet pipe, air outlet pipe, chemical dosing pipe, air compressor (1), chemical dosing device (3) and ground PLC controller (2) are tightly connected. All interfaces are tightly sealed, and 10-20 mm stainless steel corrugated pipes are used for the air inlet and outlet pipes. The well pipe and the wellbore wall are reinforced with 5-10 cm bentonite.

6. The application method of the three-dimensional well group structure for in-situ groundwater remediation according to claim 4 is characterized in that: In the horizontal water flow transmission of the large hydraulic circulation between the two groups of groundwater wells (4), the influence of water flow on the diffusion of the agent is taken into consideration and the ratio of the pumping and drainage rates of the two wells is adjusted. When the water flow rate is low, the pumping rate of the upper well is appropriately reduced and the pumping rate of the lower well is increased to maintain the horizontal hydraulic gradient between the two wells within the range of 0.005-0.01 m / m, so as to ensure that the agent can overcome the water flow resistance in the horizontal direction and fully diffuse to the area 20-30 m away from the well.

7. The application method of the three-dimensional well group structure for in-situ groundwater remediation according to claim 4 is characterized in that: In the hydraulic jump layer transmission link between the upper and lower layers, it is optimized according to the lithological characteristics of different formations. In the sandy aquifer, its porosity is conducive to the rapid penetration of water flow and reagents, and the extraction frequency is set to once every 4-6 hours. In the silty clay aquifer, the porosity is small and the hydraulic conductivity is low. The extraction frequency is adjusted to once every 8-10 hours, and the extraction power is increased by 10%-15% in stages during the extraction process, so that the reagent can effectively break through the formation resistance and realize jump layer transmission. In the case of jump layer, if the concentration of the upper layer reagent is 30%-50% higher than that of the lower layer, the extraction parameters are automatically adjusted to slow down the upper layer pumping and speed up the lower layer pumping by 10%-20%. The balanced concentration promotes the two-way uniform diffusion of the reagent and enhances the 3D hydraulic connection repair efficiency.

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